This invention relates to medical systems, and more specifically, to a medical infusion and aspiration system which provides a highly accurate, easily operated, disposable and reliable way to deliver any type of liquid or reagent with few moving parts.
There exists numerous ways to pump and aspirate liquids, beginning with a doubly open pipette and progressing to highly sophisticated electromechanical software correcting systems with many moving parts and error checking systems. Improvements in pumping systems have centered on the use of electronic controls to compensate for the mechanical limitations of current pumping systems, which generally use non-rigid materials. Many of these more sophisticated pumping mechanisms have valves and chambers that disturb the reagents normally used in such devices. The basic problem has been that in medical and other applications, there have been only a few instances where pulsatile infusion is required, and in those instances, the conventional pumping systems merely rely upon starting and stopping the pump to achieve a pulsatile regimen. Furthermore, the approach to accuracy in pumping has been to slow the device so that a precise metering could take place, which is not desired in several new medical treatments. Current products only offer pump accuracy specifications of plus- or minus 2 to 5 percent, over the entire reservoir, nor for each pulse, thereby making individual deliveries much less accurate. Thus, since there has been no apparent need for a device which could both be accurate, and still pump at a relatively high rate of flow, the field had not included a pump which can be both accurate in a pulsatile delivery, and have high rates of flow. The use of higher volumes in delivering medicines are often not medically indicated and many of the current systems have resorted to averaging out individual error to get a reportable accuracy level which is tolerable but never optimal. In fact, reporting and delivering accuracy over the entire reservoir does not deliver what the newer treatments now desire, and leads the user to believe in individual accuracy of each aliquot which in not in fact delivered.
In addition, many of the problems associated with mistakes in the delivery of medicines into patients have resulted from errors in the concentrations of the active reagent. Furthermore, most medicines have a relationship to the weight of a patient, such that their drug labels give levels of optimal administration, which should not be exceeded in the ordinary practice of medicine. Other sources of inaccurate concentrations in the delivery of medicines are the forces of ionization and collection of medicines on the surfaces of the bag or container used as a reservoir to store and deliver the medicine. The medicine can also collect on the sides of the container, and only be delivered in a relatively short period of time.
In addition to the problems discussed above, most medicines have protein or other complex molecules which are relatively easily damaged with any type of gate, valve or force which causes shearing upon the opening and closing of mechanism to stop flow. These proteins have the ability to aggregate and become ineffective, thereby giving to the patient a medicine which has changed in its effective concentration. Shear and aggregation can also occur with having flows in areas which have a high pressure.
Furthermore, many current pumping devices use syringes and have no ability to overcome the natural slip-stick or chatter associated with the storage of energy in the elastic and pliable surfaces and structures, allowing for the syringe moving face (xe2x80x9cPlungerxe2x80x9d) to move forward in irregular motions. Hysteresis and the natural tendency of plungers not to move until a force overcomes the inertia and sticking forces cause delivery of most syringe pumps to be sporadically subject so differing levels of sticking (sticktion). When these devices overcome this inertia and hysteresis, they tend to overrun and deliver at different speeds. In addition, many pumping devices vary their delivery according to the viscosity of the fluid being distributed.
Another drawback with current infusion devices is that most medicines must be withdrawn from a container, and put into the system for administration. This process requires withdrawing the medicine with a needle and then infusing the medicine into a bag or other container. The use of needles presents a hazard to the user and also introduces losses of reagent during the priming of current infusion devices.
What is needed is a medical infusion and aspiration system that avoids the disadvantages of pre-existing medical infusion and aspiration devices, that is accurate in pulsatile delivery, that is capable of high rates of flow, that provides a means to automatically avoid errors in concentrations, reagent and medicine type, that avoids the problem of shear, and other medicine degrading pressure problems, that avoids the slip-stick, chatter, overruns, and the problem of hysteresis by breaking the seating forces in a lateral motion, that does not vary the delivery profile by the viscosity of the reagent, that avoids the tendency of reagents to separate when in a diluted environment, that is inexpensive and may be used by the manufacturer in glass lined or plastic, as both the pumping cartridge and the shipping and storage cartridge, that eliminates avoids loss of reagent in the priming of the infusion device and the need for withdrawing the medicine with a needle, and that achieves extraordinary accuracy without error correcting software or expensive volumetric measurement and control systems.
Accordingly, the present invention is a medical infusion and aspiration system capable of accurate pulsatile delivery at high rates of flow. Another important characteristic of the invention is that the device provides a means to automatically avoid errors in concentration, reagent and medicine type, avoids the problems of shear and other medicine degrading pressure problems. The system also avoids the slip-stick, chatter, overruns, and the problem of hysteresis by breaking the seating forces in a lateral motion that does not vary the delivery profile by the viscosity of the reagent. The system also eliminates the tendency of reagents to separate when in a diluted environment. Other important characteristics of the invention include disposability, inexpensive cost and use by the manufacturer in glass lined or plastic, as both the pumping cartridge and the shipping and storage cartridge thus avoiding loss of reagent in the priming of an infusion device. The current invention also eliminates the need for withdrawing the medicine with a needle and achieves extraordinary accuracy without error correcting software or expensive volumetric measurement and control systems.
The current invention consists of a cassette cartridge pumping and aspirating system. The cassette cartridge contains a plunger, a reservoir area where the reagent is filled, a neck opening for the connection of the cartridge to a tube which travels to where the infusion takes place, and an in-line sensor area where probes for sampling are located. The in-line area probes are used to provide input to a pumping device. The current invention has only one moving part in relation to the delivery mechanism. Simplicity allows for more accuracy and lower costs. It also allows for a single handed adaption of the cassette to the pumping device, freeing the other hand and avoiding accidental sticking with xe2x80x9csharpsxe2x80x9d such as needles which are contaminated with blood or other materials.
In a preferred embodiment, the cartridge is cylindrical in shape and has a reservoir area, a neck opening, and encoded area. The cartridge may be made of glass, plastic steel or ceramics. It is preferable that the outer surface of the cartridge be threaded. The reservoir area is preferably used for containing a reagent and may be pre-filled, thereby enabling the seller to market pre-filled reagent cartridges. The preferred embodiment eliminates expensive residue that is thrown away with the transportation bottle, as prefilling allows for no waste. Pumps which may be re-inserted can store the unused reagent for an appropriate period of time in the cassette.
The neck opening is preferably located at the bottom surface of the cartridge and sized to connect an infusion tube to the cartridge. Any conventional tube connection device may be used to connect the infusion tube to the cartridge. The cartridge also has a cap and container top which allows the cartridge to act as the storage vessel for the reagent, and thereby avoid additional steps of filling, mixing, measuring or wasting reagent in the handling of the fluid.
In the preferred embodiment of the invention, an optical or electromagnetic strip is located within an encoded area on the cartridge. When the cartridge is filled, an optical or electromagnetic strip with information on the contents and uses of the reagent is placed in the encoded area. The encoded area is preferably located on the outer surface of the cartridge in the area that is first inserted the housing. When the cartridge is placed in the device, it is preferable that the rotational action causes the encoded area to be well aligned and easily read with the uniform motion of screwing the cartridge into place. The preferred rotation, pre-determined position of the encoded area, and the ease of programming a unique character to each cartridge allows the reagent to be mistake limiting. Furthermore, the preferred embodiment system requires a weight to be entered into a pumping device for each patient, thus greatly reducing the incidence of errors. Any conventional method of storing and retrieving data from the encoded area are preferably included in the present system to limit the incidence of errors. It is preferable that the encoded area comes into close proximity with a reading system as the cartridge is loaded or is first used. The reading system may be any commercially available system capable of reading the encoded area. A medical device stores and uses the encoded information in its operations, including a means to limit the profile of the infusion allowed without further intentional override of the profile.
In the preferred embodiment, the housing consists of a cylindrical tube that is sealed at the upper end and made from plastic. The bottom of the housing is preferably open and the inner surface of the housing is preferably threaded and sized to receive the cartridge. A plunger is preferably connected to the sealed end and is suspended in alignment with the central axis of the cylindrical tube. In the preferred embodiment, there is a plurality of openings cut through the housing to allow for normally trapped air to be exhausted as the plunger either advances or retards. The plurality of openings also creates an inspection window within the housing allowing access to the optical or electromagnetic strip within the encoded area. A lip at the bottom of the housing provides for a manually removable cover used to protect the cartridge from contamination or damage to the plunger. When the cartridge is engaged in the housing, the cartridge is locked into place by the rotational engagement of the threads. The locking of the meshed threads makes an accidental infusion by dropping or pressing on the plunger virtually impossible. The cartridge will not siphon out of the pump, or accidentally deliver fluid when dropped or pushed against.
The preferred plunger is a piston-type plunger and is preferably connected to the sealed end of the housing and is aligned with the central axis of the housing. The plunger head is preferable sized to fit the reservoir opening, so there is very little dead space thus resulting in very little loss of reagent in the final stroke or at the end of treatment.
In the preferred embodiment, a pumping mechanism is used to rotate the plunger within the cassette. The pumping mechanism comprises a gear linkage, a motor and a pumping device. The pumping mechanism may be actuated by any motor which rotably moves the plunger or housing. The present invention allows for direct drive, stepper motor, spring or band action motor, or hand articulation to deliver the desired plunger rotation. The xe2x80x9cmotorxe2x80x9d may be even a coordinated hand-eye movement or movement to a series of xe2x80x9cclickxe2x80x9d points. In a preferred embodiment, the plunger rotates in relation to the walls of the cassette housing.
In the preferred embodiment, the cartridge, when placed in the housing, causes the piston plunger to move both forward and aft to aspirate or infuse, as well as rotate within the Cassette to break the forces of inertia and slip-stick as well as eliminate backlash. Because the device avoids slip-stick, chatter and the forces of hysteresis, and has no gates or valves, it is designed to also be used in a bi-directional application, such as one of the preferred embodiments herein, where the precise amount being withdrawn may be distributed, equally or in successive steps of precise delivery, or the precise amount withdrawn re-inserted into the patient to the xe2x80x9czeroxe2x80x9d point.
A sensor area located in the infusion tube contains probes designed to determine the chemical components and levels of desired substrates in the aspirated fluids. The information obtained by the probes relayed to the pumping device and is used to control or limit the infusion profile.
The bi-directional accuracy of the present invention allows the system to be used with any number of probes. It is preferable that the probes measure the properties of a sample, such as blood, and then allow the prevent invention to re-infuse that sample back into the patient after it has been tested, or if desired, by second flow direction, deposit that blood into a separate container or depository.
The present invention also includes a pumping device. The pumping device preferably has one, two, three or more sources of input. The preferred pumping device includes, but is not limited to, an input system to drive the device, a sensor input for in-line measurement of substrates, an in-line occlusion pressure sensing system and/or input from the reading of the encoded area. The sensor input receives signals from the in-line sensor probes. The in-line occlusion pressure sensing system determines the line pressure or back pressure on the motor. Other traditional pump features are intended to be incorporated into the pumping device. In the preferred embodiment, the Rotational Velocity exceeds the Axial Velocity, although with sufficient diameter the difference in Rotational travel to Axial travel could be adjusted for the flow characteristics of the fluid to be infused and aspirated.
It is preferable that a second cassette and housing may be coupled and driven either independently or in mechanical linkage with a cassette housing so as to have as many infusion profiles, either in succession or concurrently as is desired for the given flow profiles and applications.
Since the cartridge is also the pumping system, each time the cartridge is used, it is replaced, and the entire wearing aspects of the pumping system are replaced. The product life cycles are much greater. The entire fluid handling system is replaced with each use and sterilization and cleaning of parts is eliminated.
The purpose of the present invention is to provide a system of quantitative chronoendocrinology, a term coined by the inventor. The apparent benefit to having pulses of almost any medicine, as an additional means for delivery, was deemed by the Inventors to be a valid approach to medical infusion for any and perhaps all forms of infusion therapy. Part of the invention claimed is the use of the device in sequence of infusions which, while in the aggregate the amount medicine used is less, but by virtue of the pulses, accomplishes additional medical results.